EAL

DM: Blood Glucose Self-Monitoring (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To examine the effect of 4-times daily blood glucose testing on glycemic control in subjects with stable insulin-treated type 2 diabetes.

Inclusion Criteria:

Type 2 diabetes developed after age 35 years
No history of diabetic ketoacidosis
Takes at least one injection of long-acting insulin per day
Does not self-titrate insulin doses

Exclusion Criteria:

History of alcoholism or substance abuse
Chronic liver disease
Pancreatic insufficiency
Chronic infectious disease
Endocrinopathy associated with abnormal glucose homeostasis
Recent creatinine level greater than 266 umol/dl
Received glucocorticoids or immunosuppressive drugs
Treated using insulin pump

Description of Study Protocol:

Recruitment

Subjects randomly drawn from a sample of subjects identified from computer pharmacy records at the New Mexico Veterans Administration (VA) Health Care System, the Carl T. Hayden VA Medical Center, and the Southern Arizona VA Health Care System.

Design

Prospective Cohort Study. Although subjects were instructed, prospectively, to collect data (questionaires, self-monitoring blood glucose) they were not given recommendations by the study protocol regarding medications, weight control, diet, or exercise. Subjects were entered into the study once their diabetes was considered stable for 2 months, meaning their insulin dose was not increased more than 10 units or 15% (whichever was smaller), no new oral hypoglycemic medications were started, and doses of current hypoglycemic medications were not increased.

Blinding used

Not applicable

Intervention

4-times daily SMBG

Statistical Analysis

Compliance to protocol determined by comparing number of subject blood glucose readings to number specified by protocol
Weekly average blood glucose values were determined for each mealtime and bedtime
Group differences were analyzed using X²analysis and unpaired student's t test
Within-subject changes in A1C and blood glucose were analyzed by paired Student's t test and repeated-measures ANOVA
Association between week 8 A1C and variety of clinical variables was analyzed using multiple linear regression
Additional other analyses were used including plots of residuals vs estimates and semiprobability plots and Kolmogorov-Smirnoff one-sample test
All P values <0.05 were considered significant

Data Collection Summary:

Timing of Measurements

A questionaire regarding disease complications, disabilities, treatment regimens, and dietary habits was completed by each subject at entry into the study (baseline).
A food frequency questionaire was completed by each subject at study entry.
At study entry, researchers quantified physical activity by analyzing all of each subject's routine activities; average metabolic-hours per week was calculated.
Subjects were to self-monitor blood glucose data four times per day (referred to as intensive monitoring) for the 8 weeks of the study; home glucose meters were downloaded at 4 and 8 weeks.
A1C was measured at baseline, 4, and 8 weeks.
Intensive monitoring ended at 8 weeks, however some subjects remained in the longitudinal DOVES study and had A1C measured at 24 weeks, 37 weeks, and 52 weeks.

Dependent Variables

A1C results

Independent Variables

Intensive monitoring; compliance measured by meter downloads

Control Variables

Self-care behaviors (other than glucose monitoring)
Treatment intensity
Baseline A1C

Description of Actual Data Sample:

Initial N: 247 invited to participate; 218 enrolled

Attrition (final N): 201 (94% men) for 8 weeks. 159 patients were followed for 52 weeks.

Mean Age: 65.0 ± 10 years

Ethnicity: 30% were minority

Anthropometrics

Mean body mass index was 31.9 ± 5.7 gk/m²
Average amount of exercise was 62.1 ± 63.9 metabolic-hours per week
Entry insulin dose was 66.1 ± 45.1 units per day
35% of the subjects were taking oral hypoglycemic agents
Average carbohydrate consumption was 162 ± 111 grams per day
10.5% of the subjects were taking insulin once per day
72.6% of the subjects were taking insulin twice per day

Location

Arizona and New Mexico, USA

Summary of Results:

**Effect of intensive monitoring on week 4 and week 8 A1C (N=201)**
	Baseline/Study Entry	Change from baseline at 4 weeks	Change from baseline at 8 weeks
Mean A1C %	8.10 ± 1.67	-0.30 ± 0.68 (P<0.001)	-0.36 ± 0.88 (P<0.001)

**Effect of intensive monitoring on week 8 A1C, stratified by entry A1C, and testing compliance**
	Subjects	Change	P value
By entry A1C =/< 7.0% >7.0% and =/<8.0% >8.0%	54 56 91	-0.10 ± 0.58% -0.10 ± 0.83% -0.67 ± 0.97%	NS NS <0.001
By compliance =/<60% >60% and =/<75% >75% and =/<90% >90%	33 40 58 70	-0.33 ± 0.98% -0.22 ± 1.21% -0.56 ± 0.66% -0.29 ± 0.77%	NS NS <0.001 0.003

Other Findings

The decrease in A1C persisted at week 52 in 159 subjects of the longitudinal study: A1C change from baseline -0.32 ± 1.17%, :P = 0.001.
Multiple linear regression found baseline A1C to be the strongest predictor of week 8 A1C, followed by compliance with intensive monitoring, carbohydrate intake and daily insulin dose.
Multiple linear regression analysis found age, sex, BMI, level of exercise, or use of oral hypoglycemic agents to not be predictors of week 8 A1C.

Author Conclusion:

Intensified self-monitoring of blood glucose had a clinically important and sustained effect on A1C in stable, insulin-treated veterans with type 2 diabetes.

Funding Source:

Reviewer Comments:

Potential limitations as listed in article: age population mostly older men and almost 25% of the subjects did not return for week 52, leading to possible selection bias. Intense monitoring only lasted 8 weeks. Authors note that SMBG was a powerful stimulus for changing behaviors, but it is unknown what behaviors led to improving glycemic control.

Quality Criteria Checklist: Primary Research
Relevance Questions
	1.	Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)	Yes
	2.	Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?	Yes
	3.	Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice?	Yes
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	Yes

Validity Questions
1.	Was the research question clearly stated?		Yes
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	Yes
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	Yes
	1.3.	Were the target population and setting specified?	Yes
2.	Was the selection of study subjects/patients free from bias?		Yes
	2.1.	Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?	Yes
	2.2.	Were criteria applied equally to all study groups?	Yes
	2.3.	Were health, demographics, and other characteristics of subjects described?	Yes
	2.4.	Were the subjects/patients a representative sample of the relevant population?	Yes
3.	Were study groups comparable?		N/A
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	N/A
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	N/A
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	N/A
	3.4.	If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?	N/A
	3.5.	If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.)	N/A
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	N/A
4.	Was method of handling withdrawals described?		Yes
	4.1.	Were follow-up methods described and the same for all groups?	Yes
	4.2.	Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)	???
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	4.4.	Were reasons for withdrawals similar across groups?	???
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	N/A
5.	Was blinding used to prevent introduction of bias?		Yes
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	N/A
	5.2.	Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)	Yes
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	Yes
	5.4.	In case control study, was case definition explicit and case ascertainment not influenced by exposure status?	N/A
	5.5.	In diagnostic study, were test results blinded to patient history and other test results?	N/A
6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?		Yes
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	N/A
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	Yes
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	Yes
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	Yes
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	N/A
	6.6.	Were extra or unplanned treatments described?	No
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	N/A
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	N/A
7.	Were outcomes clearly defined and the measurements valid and reliable?		Yes
	7.1.	Were primary and secondary endpoints described and relevant to the question?	Yes
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	Yes
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	Yes
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	Yes
	7.5.	Was the measurement of effect at an appropriate level of precision?	Yes
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	Yes
	7.7.	Were the measurements conducted consistently across groups?	Yes
8.	Was the statistical analysis appropriate for the study design and type of outcome indicators?		Yes
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	Yes
	8.2.	Were correct statistical tests used and assumptions of test not violated?	Yes
	8.3.	Were statistics reported with levels of significance and/or confidence intervals?	Yes
	8.4.	Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?	No
	8.5.	Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?	Yes
	8.6.	Was clinical significance as well as statistical significance reported?	No
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	N/A
9.	Are conclusions supported by results with biases and limitations taken into consideration?		Yes
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	Yes
10.	Is bias due to study's funding or sponsorship unlikely?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes